A sophisticated and flexible beam line control Graphical User Interface (GUI) has been designed and written in Tcl/Tk, which can be run under UNIX, OpenVMS and Win32 platforms. A Distributed Control System (DCS), which supports an arbitrary number of computers providing low-level hardware control at a single beam line, and simultaneous user interface clients running anywhere on the network, has also been written. The DCS is interfaced to the SSRL Instrument Control System (ICS), which is being adopted to control most of the beam line hardware on SSRL beam lines. When the protein crystallography GUI and DCS software has been fully completed, and all beam lines are equipped with state-of-the-art computer systems, it will be adopted as a standard throughout all the protein crystallography beam lines. The GUI incorporates views of each beam line component, and allows one to move each component (using either the computer mouse or command line input) and determine at a glance its exact position. The GUI also supports flexible component scanning routines.